Norio Tsuda

Performance evaluation of PTB7 : PC71BM based organic solar cells fabricated by spray coating method using chlorine free solvent

The PTB7 : PC71BM polymer based solar cells have been successfully fabricated by spin and spray coating technique using chlorine-free solvent (xylene), which are desirable to reduce environmental issues. The surface morphology of fabricated film characterized by AFM reveals that the surface morphology of the film is uniform and smooth when xylene is used as compared with chlorobenzene. The highest power conversion efficiency (PCE) (5.07 ± 0.6) was achieved using spray-coating technique than that of spin coating technique (PCE of 4.47 ± 0.6). The enhancement in the performance of the polymer solar cell could be attributed to the improved charge carrier transportation due to additive. The combination of chlorine-free solvent and spray-coating method minimize the waste material and reduce the environmental problem in large-area production of organic solar cells (OSCs).

Observation of forward breakdown mechanism in high-pressure argon plasma produced by irradiation by an excimer laser

When a XeCl excimer laser beam was focused in a high-pressure argon gas up to 150 atm, a hot and dense plasma was produced at the focal spot. The plasma developed not only backward but also forward, which differed from one produced by a visible laser. The radius of the forward plasma became smaller beyond the focal spot. There had been no explanation for the development mechanism of the forward plasma. A new model for the forward development mechanism called a forward breakdown wave was proposed. The forward plasma was calculated assuming that the laser beam transmitted through the plasma was further focused by the plasma. This model could predict the forward development behavior considerably well.

Characterization of Organic Thin Film Solar Cells of PCDTBT : PC71BM Prepared by Different Mixing Ratio and Effect of Hole Transport Layer

The organic thin film solar cells (OTFSCs) have been successfully fabricated using PCDTBT : PC71BM with different mixing ratios (1 : 1 to 1 : 8) and the influence of hole transport layer thickness (PEDOT : PSS). The active layers with different mixing ratios of PCDTBT : PC71BM have been fabricated using o-dichlorobenzene (o-DCB). The surface morphology of the active layers and PEDOT : PSS layer with different thicknesses were characterized by AFM analysis. Here, we report that the OTFSCs with high performance have been optimized with 1 : 4 ratios of PCDTBT : PC71BM. The power conversion efficiency (PCE = 5.17%) of the solar cells was significantly improved by changing thickness of PEDOT : PSS layer. The thickness of the PEDOT : PSS layer was found to be of significant importance; the thickness of the PEDOT : PSS layer at 45 nm (higher spin speed 5000 rpm) shows higher short circuit current density () and lower series resistance () and higher PCE.

Spectroscopic Measurement of High-Pressure Argon Plasma Produced by Excimer Laser

When a XeCl excirner laser beam was focused in a high-pressure gas of up to 100 atm, a hot and dense plasma was produced at the focal spot. The plasma developed not only backward but also forward. The forward plasma developed by means of a forward breakdown wave. The radius of the forward plasma becomes smaller further from the focal spot because the laser beam transmitted through the plasma was further focused by the plasma. The radiation intensity from plasma produced by an ultraviolet laser was observed using a spectrometer. The temporal spectral intensity signal had two peaks. The first peak was a signal from the plasma produced at the observed point, but the second peak was that diffused from the back. The electron temperature was measured from the ratio of the spectral intensity of Ar II lines. The electron temperature on the order of 10 5 K was obtained.

1.3-µm Quantum Dot Distributed Feedback Laser with Half-Etched Mesa Vertical Grating Fabricated by Cl2 Dry Etching

We propose a quantum dot (QD) laser with the half-etched mesa distributed feedback (HEM DFB) structure fabricated by single-step dry etching. The HEM DFB structure provides several advantages, such as low scattering loss and wavelength stability. In this study, we demonstrated a low threshold current of 23 mA and a high thermal stability of 0.077 nm/K for 1.3 µm ground state emission. We also improved the performance of the slope efficiency of HEM DFB lasers by using Cl2 dry etching.

Mechanism of forward development of a plasma produced by an excimer laser in high-pressure argon gases

In high-pressure argon gases up to 150 atm, the plasma produced by a XeCl excimer laser developed not only backward but also forward. The model for the forward development, called a forward breakdown wave, could not predict the developmental behavior in the latter stage. The development model was modified, newly taking into account the laser absorption by the plasma when the laser light was transmitted through the backward plasma. The time variation of the absorption coefficient at each distance was calculated using the inverse bremsstrahlung by the electron–ion impact. This modified model could better predict the forward development behavior than the previous model.

Characterization of the Organic Thin Film Solar Cells with Active Layers of PTB7/PC71BM Prepared by Using Solvent Mixtures with Different Additives

Organic thin film solar cells (OTFSCs) were fabricated with blended active layers of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7)/[6,6]-phenyl-C71-butyric (PC71BM). The performances of active layers are prepared in chlorobenzene (CB) with different additives of 1-chloronaphthalene (CN) and 1,8-Diiodooctane (DIO) by a wet process with spin coating technique. The effects of different solvent additives on photovoltaic parameters such as fill factor, short circuit current density, and power conversion efficiency of active layers are reported. The absorption and surface morphology of the active layers are investigated using UV-visible spectroscopy and atomic force microscopy, respectively. The results indicate that structural and morphological changes were induced by the additives with solvent. The current density-voltage (J-V) characteristics of photovoltaic cells were measured under the illumination of simulated solar light with 100 mW/cm2 (AM 1.5 G) by an Oriel 1000 W solar simulator. The OTFSCs of PTB7/PC71BM prepared with organic solvent additives of DIO

Three-Dimensional Shape and Fall Velocity Measurements of Snowflakes Using a Multiangle Snowflake Imager

AbstractThis paper describes a Multiangle Snowflake Imager (MSI) designed to capture the pseudo-three-dimensional (3D) shape and the fall velocity of individual snowflakes larger than 1.5 mm in size. Four height-offset line-image scanners estimate fall velocities and the four-angle silhouettes are used to reconstruct the 3D snowflake shapes. The 3D shape reconstruction is tested using reference objects (spheres, spheroids, cubes, and plates). The four-silhouette method of the MSI improves the representation of the particle shape and volume compared to two-silhouette methods, such as the two-dimensional video disdrometer (2DVD). The volume (equivolumetric diameters) of snowflakes estimated by the four-silhouette method is approximately 44% (13%) smaller than that estimated by the two-silhouette method. The ability of the imager to measure the fall velocity and particle size distributions based on the silhouette width and the equivolumetric diameter of 3D-shaped particles is verified via a comparison with t...

Study on laser microphone using self-couping effect of semiconductor laser for sensitivity improvement

In conventional microphone a diaphragm is used for sound wave detection. However, diaphragm limits the detectable frequency range or sound pressure range. A laser microphone which is applying self-coupling effect of LD for sound wave detection is developed. It has flat and wide frequency response by utilizing the self-coupling effect. From experiment results, laser microphone has nearly flat frequency response from 40Hz to 50kHz. However, the SN ratio decreases in low sound pressure. Therefore, actions for sensitivity improvement are subjected. Sound wave collection using parabolic sound reflector improves sensitivity. However, frequency characteristics are arisen in audible band. Light path extension using right angle prism improves sensitivity. Minimum detectable sound pressure decreases from 54dB to 47dB with light path extension.